A novel antifungal chemical has been identified that is capable of killing Trichophyton rubrum with high sensitivity. The antifungal activity is specific for dermatophyte and not other fungi. Structural characteristics of the antifungal agent that determine its activity have been identified. Human testing will be conducted to determine the effectiveness of the antifungal chemical as a topical treatment for toenail onychomycosis due to dermatophyte infection. A pilot clinical trial has revealed a mycological cure rate of 73% after three months in patients with culture positive Trichophyton rubrum toenail onychomycosis. [unreadable] Dose-response, placebo-controlled, and open trials will be conducted to determine relative mycologicai and clinical cure rates. An HPLC assay to measure the chemical will be developed and used to determine formulation stability and quality control during manufacture. Systemic levels of the drug will be determined in humans after topical use. Microbiologic assays will be conducted to determine formulation sterility following manufacture and during clinical use. If the studies are successful, topical treatment of fungal infections of nail may eliminate the need for systemic antifungal agents and their side effects for treatment of this common clinical condition. [unreadable] [unreadable] [unreadable]